I. Field of the Invention
The present invention relates to data communication. More particularly, the present invention relates to a novel and improved method and apparatus for processing a received signal based on the processing delays requirement of the communication.
II. Description of the Related Art
A modern day communications system is required to support a variety of applications. One such communications system is a code division multiple access (CDMA) system that supports voice and data communication between users over a terrestrial link. The use of CDMA techniques in a multiple access communication system is disclosed in U.S. Pat. No. 4,901,307, entitled xe2x80x9cSPREAD SPECTRUM MULTIPLE ACCESS COMMUNICATION SYSTEM USING SATELLITE OR TERRESTRIAL REPEATERS,xe2x80x9d and U.S. Pat. No. 5,103,459, entitled xe2x80x9cSYSTEM AND METHOD FOR GENERATING WAVEFORMS IN A CDMA CELLULAR TELEPHONE SYSTEM,xe2x80x9d both assigned to the assignee of the present invention and incorporated herein by reference.
A CDMA system is typically designed to conform to one or more standards. One such first generation standard is the xe2x80x9cTIA/EIA/IS-95 Terminal-Base Station Compatibility Standard for Dual-Mode Wideband Spread Spectrum Cellular System,xe2x80x9d hereinafter referred to as the IS-95 standard and incorporated herein by reference. The IS-95 CDMA systems are able to transmit voice data and (albeit not efficiently) packet data. A newer generation standard that can more efficiently transmit packet data is offered by a consortium named xe2x80x9c3rd Generation Partnership Projectxe2x80x9d (3GPP) and embodied in a set of documents including Document Nos. 3G TS 25.211, 3G TS 25.212, 3G TS 25.213, and 3G TS 25.214, which are readily available to the public. The 3GPP standard is hereinafter referred to as the W-CDMA standard and incorporated herein by reference.
The W-CDMA standard defines a channel structure capable of supporting a number of users and designed for efficient transmission of packet data. In accordance with the W-CDMA standard, data to be transmitted is processed as one or more xe2x80x9ctransportxe2x80x9d channels at a higher signaling layer. The transport channels support concurrent transmission of different types of services (e.g., voice, video, data, and so on). The transport channels are then mapped to one or more xe2x80x9cphysicalxe2x80x9d channels that are assigned to a user terminal for a communication (e.g., a call).
The W-CDMA standard allows for a great deal of flexibility in the processing of the transport channels. For example, data for a particular transport channel can be coded using a convolutional code, a Turbo code, or not coded at all. Also, the data can be interleaved over one of four different time intervals (i.e., 10 msec, 20 msec, 40 msec, or 80 msec) to provide temporal diversity against deleterious path effects (e.g., fading, multipaths, and so on). Different combinations of coding scheme and interleaving interval can be selected to provide improved performance for different types of services. For example, enhanced efficiency and performance may be obtained by processing packet data using Turbo code and a long interleaving interval, which may result in longer processing delays. In contrast, voice and video data may be processed using convolutional code and a short interleaving interval since long processing delays cannot be tolerated.
The user terminal in a W-CDMA system may receive multiple transmissions concurrently on multiple transport channels. For costs consideration, the user terminal is typically designed with one set of processing units (e.g., one decoder) for processing the transmissions. Thus, techniques that can be used to efficiently process multiple transmissions received concurrently based on their processing delays requirements are highly desirable.
The present invention provides techniques to efficiently process traffics received on multiple transport channels based on their processing delays requirements. The traffics can correspond to different types of services and may have different processing delays requirements. These delays requirements can be estimated at the receiver unit based on known parameters (e.g., fields in the traffics) or based on the manners in which the traffics have been processed (e.g., the time intervals over which the traffics have been interleaved). A controller then intelligently schedules the processing of the traffics such that the processing delays requirements are satisfied.
An embodiment of the invention provides a method for processing transmissions in a communications system (e.g., a CDMA system that conforms to W-CDMA standard, or some other system). In accordance with the method, samples are received and assembled into one or more traffics, with each traffic including one or more portions suitable for processing independently. The priority of each portion is then determined based on its processing delays requirement, and a portion in a first traffic having the highest priority is selected and scheduled for processing in accordance with a particular processing scheme. The determination of the priorities of the portions, the selection of the highest priority portion, and the scheduling of the selected portion can be repeated for each scheduling period or upon receiving an indication that another portion can be processed.
Another embodiment of the invention provides a receiver unit operative to process transmissions in a communications system (e.g., a CDMA system that conforms to W-CDMA standard). The receiver unit includes a channel processor, a buffer, a data processor, and a controller. The channel processor receives and assembles samples into one or more traffics, with each traffic including one or more portions suitable for processing independently. The buffer stores the traffics, and the data processor retrieves a particular portion of a particular traffic from the buffer and processes the retrieved portion in accordance with a particular processing scheme. The controller determines the priority of each portion stored in the buffer based on its processing delays requirement, selects a portion in a first traffic having the highest priority, and schedules the selected portion for processing by the data processor. The data processor can reorder the samples in the selected portion in accordance with a particular reordering scheme, accumulate redundant samples, and insert place holders for deleted samples. The receiver unit typically further includes a decoder that receives and decodes portions that have been processed by the data processor.
Various aspects, embodiments, and features of the invention are described in further detail below.